1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer.
2. Description of the Related Art
In recent years, improvement in performances of a thin film magnetic head is demanded in association with improvement in surface recording density of a hard disk device. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive magnetic transducer for writing and a reproduction head having a magneto resistive (hereinbelow, referred to as MR) device for reading are stacked is widely used.
One of factors which determine the performances of the recording head is throat height (TH). The throat height is a length (height) from the air bearing surface to the edge of an insulating layer for electrically isolating a thin film coil for generating a magnetic flux. The air bearing surface is a surface of a thin film magnetic head, which faces a magnetic recording medium and is also called a track surface. In order to improve the performances of the recording head, reduction in throat height is desired. The throat height is controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the recording density in the performances of the recording head, it is necessary to increase the track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface, of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve it, semiconductor processing techniques are used.
Referring to FIGS. 45 to 47, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described. Each of FIGS. 45 to 47 is a cross section orthogonal to the air bearing surface.
According to the manufacturing method, first, as shown in FIG. 45, an insulating layer 102 made of, for example, alumina (Al2O3) is deposited in thickness of about 5 to 10 xcexcm on a substrate 101 made of, for example, altic (Al2O3xc2x7TiC). Subsequently, a lower shield layer 103 for a reproduction head is formed on the insulating layer 102. For example, alumina is then deposited in thickness of 100 to 200 nm on the lower shield layer 103 to thereby form a shield gap film 104. An MR film 105 for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then a lead layer (not shown) as a lead electrode layer which is electrically connected to the MR film 105 is formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layer, shield gap film 104, and MR film 105 to bury the MR film 105 between the shield gap films 104 and 106. An upper shield-cum-bottom pole (hereinbelow, referred to as bottom pole) 107 made of a magnetic material used for both of the reproduction head and the recording head such as Permalloy (NiFe) is formed on the shield gap film 106.
As shown in FIG. 46, on the bottom pole 107, a write gap layer 108 made of an insulating film such as alumina is formed. Further, a photoresist layer 109 is formed in a predetermined pattern on the write gap layer 108 by high-precision photolithography. On the photoresist layer 109, a first thin film coil 110 for an inductive recording head made of, for example, copper (Cu) is formed by plating or the like. A photoresist layer 111 is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist layer 109 and the coil 110. In order to flatten the coil 110 and insulate turns of the thin film coil 110 from each other, a heat treatment is performed at, for example, 250xc2x0 C. A second thin film coil 112 made of, for example, copper is formed on the photoresist layer 111 by plating or the like. A photoresist layer 113 is formed in a predetermined pattern by high-precision photolithography on the photoresist layer 111 and the coil 112. In order to flatten the coil 112 and insulate turns of the thin film coil 112 from each other, a heat treatment is performed at, for example, 250xc2x0 C.
As shown in FIG. 47, in a position rearward of the coils 110 and 112 (right side in FIG. 47), an opening 108A is formed by partially etching the write gap layer 108 in order to form a magnetic path. A top yoke-cum-top pole (hereinbelow, called top pole) 114 made of a magnetic material for recording head such as Permalloy is selectively formed on the write gap layer 108 and the photoresist films 109, 111 and 113. The top pole 114 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108A. The top pole 114 is used as a mask and the write gap layer 108 and the bottom pole 107 are etched about 0.5 xcexcm by ion milling. After that, an overcoat layer 115 made of, for example, alumina is formed on the top pole 114. Finally, a slider is machined to thereby form a track surface (air bearing surface) 120 of the recording head and the reproduction head. In such a manner, a thin film magnetic head is completed.
FIGS. 48 to 50 show the structure of the thin film magnetic head in a completed state. FIG. 48 is a cross section of the thin film magnetic head perpendicular to the air bearing surface 120. FIG. 49 is an enlarged cross section parallel to the air bearing surface 120 of the pole portion. FIG. 50 is a plan view. Each of FIGS. 45 to 48 is a cross section taken along line A-AA of FIG. 50. In FIGS. 48 to 50, the overcoat layer 115 is not shown.
In order to improve the performances of the thin film magnetic head, it is important to form the head with accurate throat height TH, apex angle xcex8, pole width P2W and pole length P2L shown in FIGS. 48 and 49. The apex angle xcex8 is an angle formed between a straight line connecting corners of side faces on the track face side of the photoresist layers 109, 111 and 113 and the top face of the top pole 114. The pole width P2W defines the width of a recording track on a recording medium. The pole length P2L indicates the length of the pole. In FIGS. 48 and 50, xe2x80x9cTH0 positionxe2x80x9d denotes the edge on the track face side of the photoresist layer 109 as an insulating layer which electrically isolates the thin film coils 110 and 112, that is, a reference position 0 of the throat height TH.
As shown in FIG. 49, a structure in which side walls of the top pole 114, the write gap layer 108 and a portion of the bottom pole 107 are formed vertically in a self-aligned manner is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. As shown in FIG. 49, a lead layer 121 as a lead electrode layer electrically connected to the MR film 105 is provided on both sides of the MR film 105. In FIGS. 45 to 48 and FIG. 50, the lead layer 121 is omitted.
FIG. 51 shows the structure in plan view of the top pole 114. As shown in the diagram, the top pole 114 has a yoke 114A which occupies a major portion of the top pole 114 and a pole tip 114B having an almost constant width W1 as the pole width P2W. In the connecting portion between the yoke 114A and the pole tip 114B, the outer periphery of the yoke 114A forms an angle xcex1 to a plane parallel to the air bearing surface 120. In the connecting portion, the outer periphery of the pole tip 114B forms an angle xcex2 to a plane parallel to the air bearing surface 120. For example, xcex1 is about 45 degrees and xcex2 is about 90 degrees. The width of the pole tip 114B specifies the width of a recording track on a recording medium. The pole tip 114B includes a portion F on the front side (close to the air bearing surface 120 side) with respect to the position TH0 and a portion R on the rear side (on the yoke portion 114A side) with respect to the position TH0. As understood from FIG. 48, the portion F extends on the flat write gap layer 108, and the portion R and the yoke 114A extend on a coil portion which is covered with the photoresist films 109, 111 and 113 and is raised like a mountain (hereinbelow, called an apex portion).
The shape of the top pole is described in, for example, Japanese Unexamined Patent Application No. 8-249614.
Since the pole width P2W determines the track width of the recording head, accurate formation is required. Especially, in recent years, in order to realize high surface density recording, that is, to form a recording head of a narrow track structure, a microprocess of setting the width P2W of the top pole to 1.0 xcexcm or narrower is requested.
As a method of forming the top pole is, for example, as disclosed in Japanese Unexamined Patent Application No. 7-262519, a frame plating method is used. In the case of forming the top pole 114 by using the frame plating method, first, a thin electrode film made of, for example, Permalloy is deposited on the whole apex portion by sputtering or the like. A photoresist is then applied on the electrode film and is patterned by a photolithography process to form a frame (outer frame) for plating. By using the electrode film formed before as a seed layer, the top pole 114 is formed by plating.
There is a level difference of, for example, about 7 to 10 xcexcm between the apex portion and the other portion. A photoresist is applied on the apex portion in thickness of 3 to 4 xcexcm. When it is assumed that at least 3 xcexcm of thickness of the photoresist on the apex portion is necessary, since the photoresist having fluidity gathers in the lower portion, a photoresist film in thickness of about 8 to 10 xcexcm is formed below the apex portion.
In order to form a narrow track as described above, it is necessary to form a frame pattern having a width of about 1.0 xcexcm by a photoresist film. That is, a fine pattern having a width of 1.0 xcexcm or narrower has to be formed by a photoresist film having a thickness of 8 to 10 xcexcm or more. It is, however, extremely difficult to form such a thick photoresist pattern in width of the narrower pattern in a manufacturing process.
Moreover, at the time of photolithography, light for exposure is reflected by an electrode underlayer as a seed layer. By the reflection light, the peripheral area in the photoresist covered with a photomask is deformed or the like, so that a sharp and accurate photoresist pattern cannot be obtained. As a result, rounding of the side walls of a top pole or the like occurs, and the top pole cannot be formed in a desired shape. For example, when a positive photoresist is used as the photoresist and the pole width P2W is further reduced to W1A as shown in FIG. 52, it becomes more difficult to obtain the desired width W1A for the following reason. In the portion R extending over the apex portion of the pole chip 114B, the light reflected by the electrode underlayer includes not only reflection light in the vertical direction but also reflection light in the orthogonal or lateral direction from an inclined face of the apex portion. The reflection light exerts an influence on photosensitivity of the photoresist layer. As a result, the width of the photoresist pattern which defines the pole width P2W becomes wider than an expected value and the shape of the pole width P2W becomes as shown by a solid lines in FIG. 52. In the diagram, broken lines show the shape of a photomask used for patterning the photoresist.
In the pole tip 114B, the width of the front portion F with respect to the TH0 position is an extremely important factor of defining the track width on a recording medium. When the width of the portion F becomes wider than W2, a target fine track cannot be obtained.
For example, in order to improve the so-called NLTS (Non-Linear Transition Shift) characteristic, it is necessary to shorten the magnetic path length, that is, the length of a portion as a path of a magnetic flux generated by the thin film coil as much as possible. For this purpose, it is demanded to form the throat height TH sufficiently short. The NLTS expresses a deviation amount between an ideal magnetic recording position on a disk and an actual magnetic recording position in percentage. For example, as shown in FIG. 53, when the polishing amount at the time of forming the air bearing surface 120 is increased to make the throat height TH shorter than that in FIG. 52, the width W1B of the pole tip 114B in the air bearing surface becomes certainly wider than the width W1A of the pole tip 114B in FIG. 52. It is therefore difficult to obtain the target fine track width.
The above-mentioned magnetic head disclosed in Japanese Unexamined Patent Application No. 8-249914 also has a similar problem. In the magnetic head disclosed in the publication, the pole width changes gently from the TH0 position to the yoke. Consequently, reflection light in the orthogonal or lateral direction from the inclined face of the apex portion exerts a large influence on the photosensitivity of the photoresist layer, so that the width of the front portion with respect to the TH0 position cannot be accurately controlled.
As shown in FIGS. 52 and 53, since the rear portion R with respect to the TH0 position in the pole tip 114B has almost the same width as that of the front portion F with respect to the TH0 position and its cross-sectional area is small, the magnetic flux from the yoke 114A is saturated in the portion R and cannot sufficiently reach the portion F which defines the track width. As a result, the overwrite characteristic, that is, a characteristic in the case of overwriting data on a recording medium on which data has been already written becomes as low as about 10 to 20 dB. There is a problem such that a sufficient overwrite characteristic cannot be assured.
For example, as shown in FIGS. 54A and 54B, what is called a stitched pole type thin film magnetic head has been also proposed. In the stitched pole type thin film magnetic head, another pole tip 118A which is narrower than the pole tip 114B as a portion of the top pole 114 is formed under the pole tip 114B and the pole tips 118A and 114A are magnetically coupled to each other. In the diagram, the first thin film coil 110 is disposed on a thick insulating layer 116 formed on the write gap layer 108. In the rearward of the insulating layer 116, a magnetic layer 118B formed in the same process as the pole tip 118A is disposed. According to the thin film magnetic head, the pole tip 118A is formed on the flat write gap layer 108. It is therefore relatively easy to form the narrow pole tip 118A for defining the track width on a recording medium and the recording track width in the recording medium can be reduced. In the thin film magnetic head of this kind, however, there is a case such that the photoresist pattern in the portion, which is related to the formation of the pole tip 118A, is widened due to an influence of reflection light from the underlayer at the time of exposure. As a result, it is difficult to evenly and sufficiently reduce the width of the pole tip 118A.
The invention has been achieved in consideration of the problems and its object is to provide a method of manufacturing a thin film magnetic head capable of obtaining a sufficient overwrite characteristic by accurately controlling the pole width even when the pole width is reduced.
According to the invention, there is provided a method of manufacturing a thin film magnetic head comprising: at least two magnetic layers which are magnetically coupled to each other and include two magnetic poles which partially face each other via a gap layer on the recording medium facing side; and a thin film coil portion disposed between the at least two magnetic layers via an insulating layer, at least one of the two magnetic layers having: a first magnetic portion which extends from the recording medium facing surface to either an edge portion on the side close to the recording medium in the insulating layer or a portion near the edge portion and which defines a width of a recording track on the recording medium; and a second magnetic portion which is wider than the first magnetic portion, magnetically coupled to the first magnetic portion in or near the edge portion of the insulating layer, and extends so as to be apart from the recording medium facing surface, a step face in the width direction being formed in the coupling position of the first and second magnetic portions, a first corner being formed in an intersecting portion of a side face of the first magnetic portion and the step face, and a second corner being formed in an intersecting portion of a side face of the second magnetic portion and the step face, the method comprising: a step of forming a photoresist pattern in a predetermined-shaped portion by performing a photolithography process with a light shield mask whose basic shape corresponds to a shape of each of the first and second magnetic portions; and a step of selectively forming the at least one of the magnetic layers by using the formed photoresist pattern, wherein the light shield mask includes a predetermined-shaped portion by which a projection can be formed in a portion in the photoresist pattern, the portion corresponding to the first corner in the at least one of the magnetic layers.
In the method of manufacturing a thin film magnetic head according to the invention, a photoresist pattern in a predetermined-shaped portion is formed by performing a photolithography process with a light shield mask. Since the light shield mask has a predetermined-shaped portion by which a projection can be formed in a portion corresponding to the first corner in the at least one of the magnetic layers, because of the existence of the pattern, the exposure amount in the portion is adjusted and properly set. As a result, the photoresist pattern having the projection in the portion corresponding to the first corner in the at least one of the magnetic layers is formed. A wedge-shaped recess is formed in the first corner in the at least one of the magnetic layers obtained by using the photoresist pattern.
In the method of manufacturing a thin film magnetic head according to the invention, the predetermined-shaped portion of the light shield mask includes at least an acute angle portion.
In the method of manufacturing a thin film magnetic head according to the invention, a positive photoresist in which an area unexposed in the photolithography process remains is used as the photoresist. In this case, as the predetermined-shaped portion in the light shield mask, a projection shape which can suppress exposure in the first corner is preferable.
In the method of manufacturing a thin film magnetic head according to the invention, when a positive photoresist in which an area unexposed in the photolithography process remains is used as the photoresist, the light shield mask has a recess which can promote exposure in the second corner.
In the method of manufacturing a thin film magnetic head according to the invention, a negative photoresist in which an area exposed in the photolithography process remains may be used as the photoresist. In this case, as the predetermined-shaped portion in the light shield mask, a recess which can promote exposure in the first corner is preferable.
In the method of manufacturing a thin film magnetic head according to the invention, when a negative photoresist in which an area exposed in the photolithography process remains is used as the photoresist, further, the light shield mask has a projection shape which can suppress exposure in the second corner.
In the method of manufacturing a thin film magnetic head according to the invention, a pattern portion corresponding to the first magnetic portion in the light shield mask has a constant width.
In the method of manufacturing a thin film magnetic head according to the invention, when at least one of the magnetic layers includes a third magnetic portion which is magnetically coupled to the second magnetic portion and is wider and larger than the second magnetic portion, the first to third magnetic portions may be integrally formed by using a light shield mask having a shape corresponding to all of the first to third magnetic portions.
In a method of manufacturing a thin film magnetic head according to the invention, when at least one of the magnetic layers includes a third magnetic portion which is magnetically coupled to the second magnetic portion and is wider and larger than the second magnetic portion, the following manner is also possible. The first and second magnetic portions are formed by using a light shield mask having a shape corresponding to the first and second magnetic portions and, after that, the third magnetic portion is separately formed by using a second light shield mask having a shape corresponding to the third magnetic portion.
In the method of manufacturing a thin film magnetic head according to the invention, the light shield mask has a shape by which the direction of the step face in the coupling position can perpendicularly cross a side face in the first magnetic portion.
In the method of manufacturing a thin film magnetic head according to the invention, the light shield mask is positioned so that the position of the step face of the coupling position matches with the position of the edge on the side close to a recording medium in the insulating layer, and a photolithography process is performed.
In the method of manufacturing a thin film magnetic head according to the invention, the predetermined-shaped portion may include a recess or a projection in a right-angled triangle shape. In this case, preferably, the tip of the recess or projection in the right-angled triangle shape has an acute angle, and a depth of the recess or a height of the projection is set within a range from 0.3 xcexcm to 0.8 xcexcm.
According to the invention, there is provided a method of manufacturing a thin film magnetic head comprising: at least two magnetic layers which are magnetically coupled to each other and include two magnetic poles which partially face each other via a gap layer on the recording medium facing side; and a thin film coil portion disposed between at least the two magnetic layers via an insulating layer, at least one of the two magnetic layers having: a first magnetic portion which extends from a recording medium facing surface to either an edge portion on the side close to the recording medium in the insulating layer or a portion near the edge portion and which has a constant width that defines a width of a recording track on the recording medium; and a second magnetic portion which is wider than the first magnetic portion, magnetically coupled to the first magnetic portion in or near the edge portion of the insulating layer, and extends so as to be apart from the recording medium facing surface, a step face in the width direction being formed in the coupling position of the first and second magnetic portions, a first corner being formed in an intersecting portion of a side face in the first magnetic portion and the step face, and a second corner being formed in an intersecting portion of a side face in the second magnetic portion and the step face, the method comprising: a step of forming a photoresist pattern in a predetermined-shaped portion by performing a photolithography process with a light shield mask whose basic shape corresponds to a shape of each of the first and second magnetic portions; and a step of selectively forming the at least one of the magnetic layers by using the formed photoresist pattern, wherein the light shield mask has a shape including an acute angle portion in a position corresponding to the first corner in at least one of the magnetic layers.
According to the invention, there is provided a thin film magnetic head comprising: at least two magnetic layers which are magnetically coupled to each other and include two magnetic poles partially facing each other via a gap layer on the recording medium facing side; and a thin film coil portion disposed between the at least two magnetic layers via an insulating layer, wherein at least one of the two magnetic layers has: a first magnetic portion which extends from a recording medium facing surface to either an edge portion on the side close to the recording medium in the insulating layer or a portion near the edge portion and which has a constant width that defines a width of a recording track on the recording medium; and a second magnetic portion which is wider than the first magnetic portion, magnetically coupled to the first magnetic portion in or near the edge portion of the insulating layer, and extends so as to be apart from the recording medium facing surface, a step face in the width direction is formed in the coupling position of the first and second magnetic portions, a first corner is formed in an intersecting portion of a side face in the first magnetic portion and the step face, a second corner is formed in an intersecting portion of a side face in the second magnetic portion and the step face and, further, a wedge-shaped recess is provided in the first corner.